Chrysler Cirrus/Stratus/Sebring/Avenger/Breeze 1995-1998

Heated Oxygen Sensor

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OPERATION



As a vehicle accrues mileage, the catalytic converter deteriorates. The deterioration results in a less effective catalyst. To monitor catalytic converter deterioration, the fuel injection system uses two heated oxygen sensors: one which is upstream of the catalytic converter and one downstream of the converter.

The PCM compares the reading from the sensors to calculate the catalytic converter oxygen storage capacity and storage efficiency. The PCM also uses the upstream heated oxygen sensor input when adjusting the injector pulse width. When the catalytic converter efficiency drops below preset emission criteria, the PCM stores a Diagnostic Trouble Code (DTC) and illuminates the Malfunction Indicator Lamp (MIL).

The automatic shutdown relay supplies battery voltage to both of the heated oxygen sensors. The sensors have heating elements which reduce the amount of time it takes for the sensors to reach operating temperature.

TESTING



  1. Visually check the connector, making sure it is properly attached, and that all of the terminals are straight, tight and free of corrosion.
  2.  
  3. Allow the heated oxygen sensor to cool to room temperature.
  4.  
  5. Use an ohmmeter to test the heating element of the heated oxygen sensors:
    1. Detach the electrical connector from each oxygen sensor. The white wires in the sensor connector are the power and ground circuits for the heater elements.
    2.  
    3. Connect the ohmmeter test leads to the terminals of the white wires in the heated oxygen sensor connector.
    4.  

  6.  
  7. Replace the heated oxygen sensor if the resistance is not 5-7 ohms for 1995 vehicles or 4-7 ohms for 1996-98 vehicles.
  8.  

Before installing a new oxygen sensor, perform a visual inspection. Black, sooty deposits on the sensor tip may indicate a rich air/fuel mixture. White, gritty deposits could result from an internal antifreeze leak. Brown deposits indicate oil consumption. All of these contaminants can damage a new sensor.

REMOVAL & INSTALLATION



See Figures 1 and 2

  1. Disconnect the negative battery cable. On Cirrus, Stratus, Sebring convertible and Breeze models, disconnect the negative battery cable at the remote location on the left strut tower.
  2.  
  3. Raise and safely support the vehicle.
  4.  
  5. Unplug the upstream oxygen sensor connector.
  6.  



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Fig. Fig. 1: Disconnecting the oxygen sensor connector